1. Field of the Invention
This invention relates to a treatment method for a probe card. More particularly, this invention relates to treatment method for a cantilever probe card, which improves of the elasticity and the planarity of a cantilever probe card.
2. Description of the Related Art
After the completion of the manufacturing process of an integrate circuit (IC), the circuit fabricated on a wafer are normally tested using a multiple-point probe card. A probe card is a printed circuit board that can be used in conjunction with testing equipment to test the electrical properties of semiconductor chip devices. A typical probe card contains a plurality of probe needles. During the testing procedure, the probe needle is brought into contact (a touchdown) with the bonding pad of the test key, located on the individual circuit. The probe needles are typically applied to the test key of the wafer with sufficient force to ensure a proper contact with the bonding pad. As a result, the probe needle scratches the surface of the bonding pad, and the scratch mark on the bonding pad is used to evaluate the quality of the test. When a scratch mark is too big, the vertical position or the height of the probe needle is adjusted to maintain the quality of the test.
The cantilever probe card is one type of the probe cards used to evaluate the yield of IC devices. During the touchdown process, the cantilever probe card is subjected to an external stress. In the mean time, an internal stress and moment are generated in the probe needle to maintain a static balance of the probe needle. Since the probe needle is not an isotropic material, the internal stress is not completely dissipated even after the external stress is removed. After thousands of touchdown processes, the residual stress gradually accumulates in the probe needle, causing the probe needle on the probe card to lose its elasticity. Consequently, the position of the probe needle is shifted during a touchdown process. Furthermore, the residual stresses in different probe needles are different; the probe needles on the probe card therefore do not return to the same planar surface by the elasticity of the probe needles. A reduction of the planarity of the probe needles is hence resulted.
A method to restore the shifted position and the reduction of planarity of the probe needle is to adjust the test parameters of the probe needles. For example, the preset height of the probe is lowered from 55 microns above the common IC plane to 45 microns so that the test can be continued without the probe needle recovering its original elasticity. However, after the test is continued for a period of time, the probe needle suffers fatigue, and the problems of the shifted position and the reduction of the planarity of the probe needle will occur repeatedly. Furthermore, in order to adjust the position of the probe needles, an operator is required to manually adjust the probe needle to the proper position. This approach not only is time consuming, but also damages the probe card easily. Replacement with a new probe card is then needed, leading to an increase of the production cost.
In addition, the border of the wafer is usually curved, which easily causes the probe needle to bend. This type of damage to the probe needle also requires replacement with a new probe card, which again leads to an increase of the production cost.